说明：  二维情况下用ＦＤＴＤ方法模拟电磁波的传播情况，没加吸收边界条件，用Ｃ和MATLAB混合编程，信号源是高斯脉冲
(Two-dimensional case with the FDTD simulation of electromagnetic wave propagation, no additional absorbing boundary condition, mixed with the C and MATLAB programming, the signal source is a Gaussian pulse)